The present invention relates to a multi-direction switch for use in an input operation part of a portable telephone or the like.
Among multi-direction switches of this kind is, for example, a four-direction switch with a center click. The four-direction switch has a total of five switch contacts disposed at the center and at four positions around (front-rear and right-left) and is designed to actuate the central switch contact by manual depression of the keytop at the center thereof and a desired one of the others (peripheral switch contacts) by tilting the keytop in the direction corresponding thereto.
FIG. 1A depicts the four-direction switch with a center click which is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-331329. In this prior art example, a central movable contact 12 and peripheral movable contacts 13 are disposed above a printed wiring board 11 on which there are formed plural pairs of spaced apart but adjacent stationary contacts (not shown). Overlying the movable contacts 12 and 13 is a keytop 14.
The central movable contact 12 is made of a resilient metal sheet press-worked in the shape of a dome. When pressed at the top, the central movable contact 12 flips into contact with the pair of stationary contacts corresponding thereto, establishing electrical connections between them. As a result, the central switch is turned ON. The flipping action provides good tactile response with a click.
On the other hand, the peripheral movable contacts 13 are each formed, for instance, by a strip of sheet metal having its outturned both ends fixed to the printed wiring board 11 with the intermediate portion spaced a required distance away from the pair of stationary contacts in parallel face-to-face relationship therewith. When depressed, the intermediate portion is elastically deformed into contact with the pair of stationary contacts. The central and peripheral movable contacts 12 and 13 are secured to the printed wiring board 11 by pasting thereto a single-sided adhesive sheet 15 from above.
The keytop 14, which is received in an opening 19 of a housing 17, has a laterally directed peripheral flange 16 continuous with the lower edge thereof for engagement with an engagement portion of the housing 17 to prevent the keytop 14 from falling off.
On the underside of the keytop 14 there are provided a central press protrusion 21 corresponding to the central movable contact 12 and peripheral press protrusions 22 corresponding to the respective peripheral movable contacts 22. As depicted in FIG. 1A, when the keytop 14 is not pressed, the central press protrusion 21 and the central movable contact 12 are in resilient contact, by which the flange 16 is resiliently pressed against the engagement portion 18. The central press protrusion 21 downward from the bottom surface of the keytop 14 is higher the respective peripheral press protrusion 22.
In the conventional multi-direction switch of the above construction, the depression of the keytop 14 at the center thereof causes the central movable contact 12 to flip into contact with the underlying stationary contact pair, turning ON the central switch. At this time, since the peripheral press protrusions 22 is lower than the central protrusion 21, none of the peripheral movable contacts 13 contact the stationary contact pairs, that is, no peripheral switches turn ON.
However, when the keytop 14 is pressed at its marginal edge to turn ON a desired one of the peripheral switches, the keytop 14 tilts or pivots about the engagement portion 18 of the housing 17 on the side diametrically opposite the marginal edge of the keytop 14 being pressed. As a result, the peripheral movable contact 13 on the side of the marginal edge being depressed is pressed by the corresponding peripheral press protrusion 22 but, at the same time, the central movable contact 12 is also pressed by the central press protrusion 21, and if too much deformed, the central movable contact 12 will flip and hence turn ON the central switch.
This leads to unnecessary manipulation of the central switch and requires increased force for pressing the keytop 14 accordingly and generates a click feel, too, badly impairing the operating feel and hence giving rise to a problem in ease of use.
It is therefore an object of the present invention to provide a multi-direction switch that prevents the possibility of the central switch being turned ON simultaneously by the manual operation for actuating (turning ON) the peripheral switch, and hence has excellent usability.
According to the present invention, there is provided a multi-direction switch which is provided with a central switch and a plurality of peripheral switches arranged about said central switch and in which a desired one of said switches is actuated by pressing a keytop, said multi-direction switch comprising:
a printed wiring board having formed thereon a central stationary contact and a plurality of peripheral stationary contacts arranged circumferentially about said central stationary contact;
a dome-shaped central movable contact disposed above said central stationary contact in opposing relation thereto and constituting said central switch together with said central stationary contact;
peripheral movable contacts each disposed above one of said peripheral stationary contacts in opposing relation thereto and constituting one of said plurality of peripheral switches together with the corresponding one of said plurality of peripheral stationary contacts;
a frame having a central plate portion disposed above said central movable contact, a plurality of legs bent form the periphery of said central plate portion toward said printed wiring board, and a fulcrum portion provided on the underside of said central plate portion, said frame being fixed to said printed wiring board;
a keytop disposed above said frame;
a housing having an opening for receiving said keytop and fixed to said printed wiring board; and
a pusher having a base opposite the underside of said keytop with said central plate portion of said frame sandwiched therebetween, a plurality of arms extended radially from said base and fixed to the underside of said keytop, an engagement portion formed in the top surface of said base centrally thereof for pivotable engagement with said fulcrum portion of said frame, and a central press protrusion provided on the underside of said base centrally thereof opposite said central movable contact;
wherein the top surface of said base of said pusher and the bottom surface of said keytop define therebetween a gap for receiving said central plate portion of said frame in a manner to permit pivotal movement of said keytop.
With the above arrangement, the keytop pivots about substantially the center of the keytop where the frame and the pusher engage, not about the marginal edge of the keytop diametrically opposite the pressed edge as in the prior art; therefore, the peripheral and central switches are not likely to turn ON at the same time.
In the above multi-direction switch, a peripheral press protrusion may be provided on the underside of each arms of the pusher or on the underside of the keytop in opposing relation to one of the peripheral movable contacts, or
In the above multi-direction switch, a plurality of retaining pieces are protrusively provided on the inner peripheral surface of the opening of the housing, the plurality of legs of the frame are bent outwardly in L-letter form, and the tip ends of the plurality of legs of the frame are fixedly held between the plurality of retaining pieces and the printed wiring board.
Alternatively, there is held between the housing and the printed circuit board a mounting plate which has cut therethrough a slit centrally thereof for receiving the base of the pusher and has secured thereto the central plate portion of the frame across the slit by the plurality of legs of the frame. And the peripheral press protrusions provided on the underside of the keytop are disposed opposite the peripheral movable contacts through the slit of the mounting plate. This structure permits reduction of the thickness of the multi-direction switch.
Alternatively, there is held between the housing and the printed wiring board an elastic sheet which has an opening bored therethrough centrally thereof for receiving the pusher and an annular ridge formed along the marginal edge of the opening and fitted in an annular groove cut in the underside of the keytop. This structure prevents the intrusion of foreign substances into the pivotal mechanism.
Alternatively, there are provided a mounting plate which has an annular portion and a plurality of frame support protrusions protruding from the inner marginal edge of the annular portion toward the center thereof for supporting the base of the frame disposed at the center of the mounting plate with the plurality of legs of the frame fixed to the plurality of frame support protrusions, and a double-sided adhesive sheet having its central portion cut out for bonding the annular portion of the mounting plate to the printed wiring board, the peripheral press protrusions of the keytop and the pusher lying in the cut-out area of the double-sided adhesive sheet. This structure allows ease in assembling the multi-direction switch.